Light-sensitive imaging materials

ABSTRACT

Light-sensitive imaging materials contain a photo-activator capable of yielding a free radical by action of light and a normally-oxidizable, color-developing compound which is rendered incapable of oxidation, and thus not color-developing, by reaction with the free radical. Light exposure and treatment with an oxidizing agent renders positive image.

United States Patent Hoshino et al.

[4 1 Nov. 13, 1973 LIGHT-SENSITIVE IMAGING MATERIALS Inventors: Sholchlro Hoshino, Tokyo; Kellchl Yumlkl; Toshio Taira, both of Hachioji-shi, all of Japan Keuffel & Esser Company, Hoboken, NJ.

Filed: Sept. 26, 1968 Appl. No.: 763,005

Assignee:

Foreign Application Priority Data Sept. 28, 1967 Japan 42/62114 US. Cl 96/48 R, 96/90 R, 96/88 Int. Cl G03c 5/24 Field of Search 96/48 R, 90 R, 88

References Cited UNITED STATES PATENTS 1/1970 Schenk et al. 96/90 X FOREIGN PATENTS OR APPLICATIONS 957,192 5/1964 Great Britain 96/90 Primary ExaminerNorman G. Torchin Assistant ExaminerWon H. Louie, Jr.

Att0rney.l. Russell Juten, Peter F. Willig, Lionel N. White and Milford A. Juten [57] ABSTRACT 8 Claims, No Drawings LIGHT-SENSITIVE IMAGING MATERIALS BACKGROUND OF INVENTION and electrophotographic copying papers using a photoelectroconductive material.

However, these copying papers individually have their merits and demerits. For example, the lightsensitive copying papers for silver halide diffusion transfer process are markedly high in sensitivity but are expensive due to complexity in steps for the production thereof, and operations for the development thereof are also complex. The diazo copying papers are low in cost but, in developing the papers, a high concentration alkali developer or an ammonia gas strong in irritating odor should undesirably be used. Moreover they are poor in storability since diazo compounds are hydrophilic, in general, and hence are susceptible to temperature variation. Further, the electrophotographic copying papers have such drawbacks that the copying step thereof is markedly complex and the machine to be used for the copying thereof is quite expensive. Accordingly, there have been desired copying papers for business which can overcome the above-mentioned drawbacks, and which are high in light sensitivity, simple to use so as to require no particular skill, low in cost and high in quality.

There have heretofore been proposed copying papers in which are used such light-sensitive organic substances as, for example, naphthols (US. Pat. No. 3,094,417), halogen compounds capable of yielding free radicals by action of light (US. Pat. Nos. 3,042,515 and 3,042,519), aromatic dialdehydes (US. Pat. No. 3,102,811) and light-sensitive leuco cyanides.

These conventional copying papers, however, have not proved satisfactory in color-developing property, storability, fixing property and toxicity.

SUMMARY OF INVENTION The present invention comprises .a light-sensitive printing material containing a photo-activator capable of yielding a free radical by action of light, and a normally oxidizable compound which develops a distinct color change upon oxidation, but which loses its colordeveloping ability by action of said free radical. That is, when the light-sensitive printing material in accordance with the present invention is subjected to contact printing by application of light, the free radical released by the photo-activator at portions which have been exposed to light brings about a photochemical reaction corresponding to the degree of exposure, though no substantial change in appearance of the material is observed. The free radical reacts with the oxidizable, color-developing compound to produce, in direct proportion to the degree of exposure a form of that compound which is to a greater degree incapable of oxidizing to effect a color change; for example, an undimerized form of compound. On the other hand, at unexposed portions upon which the light has not acted and at portions which have received less than complete exposure, the oxidizable color-developing compound is left unchanged in inverse proportion to the degree of exposure and remains, in the light-sensitive layer, as a posiposi image, though the image is not clearly visible to the eye. This positive image, when treated with such oxidizing agents develops a distinct color change to form a clear image.

DESCRIPTION OF INVENTION The photo-activators and oxidizable, colordeveloping compounds employed in the present invention are not particularly complex, as shown below, and are easily obtainable. Furthermore, they are low in cost.

Typical as the photo-activators capable of yielding free radicals by action of light, which are used in the present invention, are such compounds as enumerated below.

(I) Compounds represented by the general formula trichloro-2-methyl-2-propanol.

(II) Compounds represented by the general formula wherein R represents a hydrogen atom or 1 to 5 substituents on the benzene nucleus which are any of nitro, halogen, alkyl, haloalkyl, acetyl, haloacetyl, alkaryl and alkoxy groups, and not all of the substituents are required to be same. These compounds include, for example,

o-nitro-a,a,a-tribromoacetophenone, m-nitro-a,a,a-tribromoacetophenone, p-nitro-a,a,a-tribromoacetophenone, 01,0:,a-tribromacetophenone, a,a,a-m-tetrabromoacetophenone, a,a,a-tribroms-3,4-dichloroacetophenone, a,a,a-p-tetrabromoacetophenone, and a,a,a,a,a,a-hexabromo-p-diacetylbenzene.

(III) Compounds represented by the general formula wherein R is any of alkyl and aryl groups (including those having substituents); and X is a halogen atom.

These compounds include, for example,

1,3-benzenedisulfonyl chloride, 2,4-dinitrobenzenesulfonyl chloride,

o-nitrobenzenesulfonyl chloride,

m-nitrobenzenesulfonyl chloride,

ethylsulfonyl chloride,

p-bromobenzenesulfonyl chloride,

p-nitrobenzenesulfonyl chloride,

p-iodobenzenesulfonyl chloride,

p-acetarnidebenzenesulfonyl chloride,

p-chlorobenzenesulfonyl chloride p-toluenesulfonyl chloride,

methanesulfonyl chloride,

benzenesuifonyl chloride,

m-nitrobenzenesulfonyl fluoride, and benzenesulfonyl bromide.

(IV) Compounds represented by the general formula wherein R is any of alkyl and aryl groups (including those having substituents); and X is a halogen atom. These compounds include, for example, 2-4-dinitrobenzenesulphenyl chloride, and onitrobenzenesulfonyl chloride.

(V) Compounds represented by the general formula wherein A is a heterocyclic compound residue which may have a substituent; and R R and R are hydrogen, chlorine and bromine atoms, and not all of them are hydrogen atoms at a same time. These compounds include, for example,

m,w,m-tribromoquinaldine,

m,m-dibromoquinaldine, 2-m,m,m-tribromomethyl-4-methylquinoline, m,m-dichloromethylquinoline,

m-brornolepidine,

2-w-bromomethylisoquinoline, 4-m,m,m-tribromomethylpyrimidine, 4-phenyl-6-w,unw-tribromomethylpyrimidine, 2-m,w,w-trichloromethyl--nitrobenzothiazole, 1-phenyl-3-w,w,w-trichloromethylpyrazole, w,w,w-tribromolepidine-bromomethylate, a-cu,m-dibromomethyl-4-chloropyridine, l-methyl-2-chloromethylbenzimidazole, and 2,5-di-tribromomethyl-3,4-dibrornothiophene.

(VI) Compounds represented by the general formula distinct color changes by treatment with oxidizing agents. Compounds which are effectively usable in the present invention can be readily determined according to the following test method.

20 mg. of a sample is dissolved in 2 cc. of water or an organic solvent such as acetone or methanol. A filter paper is impregnated with the thus formed solution and is then dried. Subsequently, the paper is dipped in an aqueous solution containing 1-5 percent of potassium ferricyanide. If, in the above case, the filter paper undergoes a change in color, the sample compound may be used in the present invention. However, said compound should further pass the following test: 005g. of the said compound and 0.l5g. of hexabromodimcthyl sulfone are dissolved in 5cc. of an organic solvent such as acetone or methanol. The solution is applied to a baryta paper, and is than dried. Subsequently, the paper is exposed to ultraviolet light and is then treated with an oxidizing agent. If, in this case, the difference between exposed portions and unexposed portions is sufficient to form an image, the said compound can be effectively used in the present invention.

Typical of oxidizable compounds which are useful in the present invention are the compounds shown below. However, compounds usable in the present invention are not limited only to these.

(l). a-Naphthol M.P. 94 C.

-methoxy-a-naphthol Ml. C.

( 4bromo--naphth0l My. 127128 C.

(6). 2,4-dlbr0mo-a-naphth0l M-P- 111 C- (7). .Z,4(lluhloro-mnuplitllol M-P- 106 C.

(8).. on 4-acetarni11o-a-naphth0l M-P- 187 C- O H s NH O 0 CH3 (9)- 4-thiocyano-a-naphth0L M.P- 113-114 O.

CNS

(10) i-methylthio-a-naphthol M.P. 116 0.

S C H;

(11). l-methoxy-tamlno-naphthalene sulfate. M.P. 115118 C.

O CH3 NHgH'JSO4 (12) Ind0xyl M.P. 85 C.

(14) Thiaindoxyl M1. 71 C.

/CH: s

(15) B-cliloro-7-meghyl-thiaindOXYl M.P.106108 0 /CH: S

(16)... i-methyl-fi-bromo-thiain xyl M.P.134 C.

The light-sensitive material according to the present invention contains, as main components, at least one photo-activator and oxidizable, color-developing compound as mentioned above, and may further be incorporated with color toners, oxidation accelerators, sensitizers and the like. Ordinarily, the optimum weight ratio of photo-activator to oxidizable, color-developing compound is 3 l, but may be suitably varied depending on the kind of compounds employed. Effective as the sensitizers may be any of those which are usable for light-sensitive silver halide photographic materials, such as xanthene dyes, eg erythrosine and eosine, and cyanine dyes (including derivatives).

The light-sensitive printing materials of the present invention may be prepared by dissolving the compo-' nents mentioned above in water or suitable solvents and applying the solutions onto supports, followed by drying. If desired, high molecular weight compounds, which are soluble in solvents and excellent in filmforming ability, may be used as binders. Typical as such high molecular weight compounds suitable for the above purposes are vinyl acetate-maleic anhydride copolymers, methyl vinyl ether-maleic anhydride copolymers, ethylene-maleic anhydride copolymers, vinyl pyrrolidone, ethylene glycol polymer, and gelatine. The solvents for the aforesaid components may be suitably selected taking dangerousness, drying property and workability into consideration. Usable as volatile solv vents other than water are alcohols such as methanol,

ethanol and propanol, ketones such as acetone and methylethylketone, aromatic hydrocarbons such as benzene, toluene and xylene, halogenated hydrocarbons such as methylene chloride and trichloroethylene, tetrahydrofuran, dimethylformamide, and cyclohexane.

Procedures for preparing the light-sensitive printing materials of the present invention are as follows:

In a state shielded from direct light, the photoactivator, the oxidizable, color-developing compound and desired additives are dissolved or dispersed in a solution containing the binder component. The resulting solution or dispersion is applied onto a support according to such a coating method as dipping, doctor or reverse roll method, followed by drying. The above operations may be effected under a yellow safety lamp. In place of dissolving or dispersing the components in a solvent, the components in the form of fine powders may be rubbed in a support, or may be added when using paper supports, during the paper-making process. As supports, various plastics films, papers and glass plates may be used. Baryta papers and plasticcoated papers are particularly useful and exceptional positive images good in resolution and high in intensity can be obtained with these materials.

For exposing the materials of the present invention any light source may be effectively used which emits a light having a wave length of about 3,4005,000 A, since the light-sensitive printing material of the present invention is sensitized with a light having a wave length within said range. Accordingly, the present lightsensitive material can be printed according to front copying using ultraviolet light, reflex copying using daylight, and enlarge-copying using a tungsten lamp. Thus, in the case of front copying, a commercially available diazo copying machine (with a mercury lamp) can be used as it is; in the case of reflex copying,

an exposing apparatus for diffusion transfer copying paper can be used; and in the case of enlarge copying, a photographic enlarger or a slide projector can be used.

The light-sensitive printing material bearing the lightformed latent image is then subjected to developing treatment with an oxidizing agent, whereby a distinct color change is obtained and the latent image becomes a permanently visible image. Effective as such oxidizing agents usable in said developing treatment may be any of those which, in general, quickly bring about oxidation reactions and which do not decolor dyes formed by the oxidation. Particularly preferable oxidizing agents are those which have not themselves colored or which are only slightly colored. Typical examples of useful oxidizing agents are potassium bichromate, sodium bichromate, ammonium bichromate, chromic anhydride (chromium trioxide), potassium permanganate, potassium ferricyanide, sodium ferricyanide, ferric chloride, potassium chlorate, potassium nitrate, nitric acid, hydrogen peroxide, sodium peroxide, barium peroxide, lead peroxide, lead nitrate, sodium nitrate, sodium chlorate, potassium peroxide, cupric chloride, potassium persulfate, ammonium persulfate, sodium hypochlorite, zinc permanganate, sodium permanganate, barium permanganate, ozone, bromine, chlorine and iodine. In treating the light-sensitive printing materials of the present invention with the above-mentioned oxidizing agents, the said materials are ordinarily treated for about -30 seconds with the oxidizing agents in the form of solutions in water, aqueous alkaline solutions or aqueous acidic solutions, or in the form of gases.

The concentration of the aqueous oxidizing solution varies depending on the kind of the oxidizing agent, but is preferably from 1 to percent by weight. For example, in case potassium ferricyanide is to be used as the oxidizing agent, an aqueous solution containing 1 percent of potassium ferricyanide sufficiently displays oxidizing ability.

PREFERRED EMBODIMENTS The following examples illustrate the present invention. Example 1 In a state shielded from direct light, I g. of 4- methoxy-a-naphthol and 3 g. of tribromomethyl sulfone were dissolved in cc. of methanol. The solution was applied to a photographic baryta paper in an amount of 30 cc. per square meter and was dried at room temperature to obtain a light-sensitive printing material. The thus obtained light-sensitive material was closely contacted with a photographic positive and was exposed for 5 seconds to a tubular 800 w high pressure mercury lamp at a distance of 5 cm. The exposed material was dipped for 10 seconds in a developer prepared by dissolving 5 g. of potassium ferricyanide in lOO cc. of water, whereby a deep blue positive image was obtained. When washed with water, the positive image became a stable image. The light-sensitive material of this example is high in sensitivity, excellent in resolution and clear in color tone, as compared with commercially available diazo copying papers. Example 2 In a state shielded from direct light, I g. of lmethoxy-4-amino-naphthalenesulfate and 3 g. of hexabromodimethyl sulfone were dissolved in an acetonemethanol l I) mixed solvent. The solution was applied according to an ordinary procedure onto a I50 g. baryta paper in an amount of 30 cc. per square meter and was then dried to prepare a light-sensitive printing material. The thus prepared light-sensitive material was exposed in the same manner as in Example 1, was dipped for 10 seconds in a 5 percent aqueous sodium bichromate solution, and was then washed with water, whereby a clear, purple, stable image was obtained. Example 3 In place of the l-methoxy-4-amino-naphthalenesulfate used in Example 2, the equivalent amount of 4- ethoxy-a-naphthol was employed to form a solution. The solution was applied onto a paper, which had been surface-treated with polyvinyl alcohol, to prepare a light-sensitive printing material. This light-sensitive material was subjected to the same exposure and developing treatment as in Example 1, whereby a clear image was obtained. The light-sensitive material of this example is for the posiposi process, and therefore it gives a negative image when a negative is used as original and forms a positive image when a positive is used as original. Example 4 In a state shielded from direct light, 1 g. of 2,4- dibromo-a-naphthol and 3 g. of hexabromodimethyl sulfone were dissolved in 100 cc. of an acetonemethanol (1 z mixed solution containing 2 percent of ethylene glycol polmer resin. The solution was applied, according to an ordinary procedure, onto a base paper commonly used to prepare diazo copying paper in an amount of 30 cc. per square meter and was then dried to prepare a light-sensitive printing material. This lightsensitive printing material was closely contacted with a photographic positive, was exposed by means of a com mercially available diazo copying machine, and was then developed for 10 seconds with a 10 percent aqueous ammonium bichromate solution, whereby a clear deep blue image was obtained. This image was washed with water to obtain a permanently stable image, which did not cause, thereafter, any change in color even when exposed to strong ultraviolet light. Example 5 Example 4 was repeated, except that tribromomethylphenyl sulfone was used in place of the hexabromodimethyl sulfone, whereby a clear, deep blue image was obtained.

Example 6 In a state shielded from direct light, lg. of 4-methoxya-naphthol and 3 g. of hexabromomethyl sulfone were dissolved in 100 cc. of an acetone-methanol (l 1) mixed solution containing 2 percent of vinyl acetatemaleic anhydride copolymer resin. The solution was further charged with 0.5 cc. of a methanol solution containing 2 percent of Acridine Orange. The solution is applied to a 150 g. photographic baryta paper in a proportion of 30 cc. per square meter and was then dried to obtain a light-sensitive printing material. To this light-sensitive material was projected for 1 minute a 35 mm. microfilm, using a 300 w slide projector at a distance of 50 cm, and then the same developing treatment as in Example 1 was effected to obtain a clear, blue, enlarged image.

Example 7 Example 1 was repeated, except that indoxyl was used in place of the 4-methoxy-a-naphthol, to prepare a light-sensitive printing material. This light-sensitive material was exposed in the same manner as in Example l and was then developed in an atmosphere of iodine gas, whereby a blue image was obtained.

The above examples have been presented for the purpose of illustration and should not be taken to limit the scope of the present invention. It will be apparent that the described examples are capable of many variations and modifications which are likewise to be included within the scope of the present invention as set forth in the appended claims.

What is claimed is:

1. An imaging process comprising:

a. exposing irnagewise to light material comprising a support and a coating thereon of light-sensitive composition consisting essentially of l an organic a-naphthol; 4-acetamino-a-naphthol; fiihiocyano a-naphthol; and 4-methylthio-a-naphthol; and thereby irnagewise forming said free radical in reactive association with said normally oxidizable compound in said composition, thus irnagewise rendering said compound incapable of normal color-changing oxidation; and

b. treating said material thus exposed with an oxidizing agent, whereby said normally oxidizable compound situated in the unexposed portions of said composition, and thus remaining normally oxidizable, is oxidized to yield said distinct color change, thereby providing a visibly distinct image.

2. The process according to claim 1 wherein said treating step comprises contacting said material with a fluid oxidizing agent.

3. The process according to claim 2 wherein said oxidizing agent comprises a solution of an oxidizing compound.

4. The process according to claim 2 wherein said oxidizing agent is a gas.

5. An imaging process comprising:

a. exposing irnagewise to light material comprising a support and a coating thereon of light-sensitive composition consisting essentially of (1) an organic halogen-containing photoactivator capable of forming a free radical by action of light and (2) a compound normally oxidizable to effect a distinct color change therein, said normally oxidizable compound being selected from the group consisting of indoxyl; -bromo-indoxyl; thiaindoxyl; 5- chloro-7-methyl-thiaindoxyl; 4-methyl-6-bromothiaindoxyl; and thereby irnagewise forming said free radical in reactive association with said normally oxidizable compound in said-composition, thus irnagewise rendering said compoundincapable of normal color-changing oxidation; and

b. treating said material thus exposed with an oxidizing agent, whereby said normally oxidizable compound situated in the unexposed portions of said composition, and thus remaining normally oxidizable, is oxidized to yield said distinct color change, thereby providing a visibly distinct image.

6. The process according toclaim 5 wherein said treating step comprises contacting said material with a fluid oxidizing agent.

7. The process according to claim 6 wherein said oxidizing agent comprises a solution of an oxidizing compound.

8. The process according to claim 6 wherein said oxidizing agent is a gas. 

2. The process according to claim 1 wherein said treating step comprises contacting said material with a fluid oxidizing agent.
 3. The process according to claim 2 wherein said oxidizing agent comprises a solution of an oxidizing compound.
 4. The process according to claim 2 wherein said oxidizing agent is a gas.
 5. An imaging process comprising: a. exposing imagewise to light material comprising a support and a coating thereon of light-sensitive composition consisting essentially of (1) an organic halogen-containing photoactivator capable of forming a free radical by action of light and (2) a compound normally oxidizable to effect a distinct color change therein, said normally oxidizable compound being selected from the group consisting of indoxyl; 6-bromo-indoxyl; thiaindoxyl; 5-chloro-7-mEthyl-thiaindoxyl; 4-methyl-6-bromo-thiaindoxyl; and thereby imagewise forming said free radical in reactive association with said normally oxidizable compound in said composition, thus imagewise rendering said compound incapable of normal color-changing oxidation; and b. treating said material thus exposed with an oxidizing agent, whereby said normally oxidizable compound situated in the unexposed portions of said composition, and thus remaining normally oxidizable, is oxidized to yield said distinct color change, thereby providing a visibly distinct image.
 6. The process according to claim 5 wherein said treating step comprises contacting said material with a fluid oxidizing agent.
 7. The process according to claim 6 wherein said oxidizing agent comprises a solution of an oxidizing compound.
 8. The process according to claim 6 wherein said oxidizing agent is a gas. 